<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>NaN</title>
</head>
<body>
    <script>
    //     console.log(NaN,typeof NaN);// NaN number
    //     console.log(0/0,-6/0); // NaN  -Infinity 
    //     console.log(Math.sqrt(-1)); // NaN
    //     console.log("abc"-10); // NaN
    //     console.log(undefined+5); // NaN
    //     console.log(parseInt("hello")); // NaN
           const a = 0/0;
           const b = parseInt("hello");
           if(Number.isNaN(parseInt("hello"))){
            console.log("hello 不是一个数字,不能继续计算了");
           }
     </script>
</body>
</html>